Science, Technology, Engineering, and Mathematics Books

Extra Special Pi Day

Tomorrow – Saturday, March 14 – is a historic day. It’s Albert Einstein’s birthday for which, if he were still alive, he’d have 136 candles on his cake.

It’s also Pi Day. March 14.

3.14. Get it?

But this year, Pi Day is extra special because it’s 2015, which means tomorrow is 3.1415. And if you chow down on a slice of pizza at 9:26 and 53 seconds – either for breakfast or a bedtime snack – you get even more Pi: 3.141592653.

You won’t see that again for another hundred years.

Back in 250 BC, Archimedes worked out that the value of pi is greater than 223/71 but less than 22/7. He did this by approximating the area of a circle using the area of a regular polygon inscribed within the circle and the area of a polygon within which the circle was circumscribed. He started with a hexagon and worked his way up to a 96-sided polygon, getting really close to the approximation of pi.

You can do that too, by comparing the ratio of a circle’s circumference (distance around) to its diameter (distance across). Put in math language, π = c/d.

All you need are a tape measure (or string), a ruler, a pencil and paper, a calculator and a few round things: soup cans, the compost bucket, cheerios, m&m’s, a cocoa mug, cookies, marshmallows, cupcakes, a pizza….

Use the tape measure or string to measure the distance around your object (circumference). Now measure the diameter (the distance from one side to the other, through the middle of the circle). Divide C by d to get … oh, perhaps you didn’t get 3.14159. Not a problem – compare the circumference and diameter of another round thing. And another. Do any of them come close? If you get 3.14 you’re doing well.